1. Field of the Invention
The present invention relates to an air pump, and more particularly to an air pump which is easily installed.
2. Description of Related Art
An air pump for inflating tires is generally composed of a body and a motor mounted on the body. The body has a gear assembly and a piston provided therein. The gear assembly has two gears engaged with each other, wherein a first gear is mounted on an output axle of the motor, and a second gear is eccentrically connected to the piston by a linkage. The piston is movably received in a sleeve mounted in an opening at a top of the body. A one-way discharge valve is mounted on the sleeve and in communication with the sleeve.
When the motor is actuated, the gear assembly is rotated to reciprocate the piston in the sleeve, so air flows in the body and is compressed in sleeve and then discharge out from a nozzle of the valve.
However, in assembly, the sleeve is directly installed in the opening in tight fit. Therefore, the sleeve should be formed with a large thickness of inner wall for ensuring good roundness of the sleeve, so the sleeve has a high cost.
Furthermore, because the sleeve is tightly received in the opening, it is difficult to control the sleeve installed in the correct position, so the piston is not coaxial with the sleeve. Thus, air in the chamber may leak out to cause an inadequate air capacity. In the reciprocation of the piston, the friction between the piston and sleeve is large so that a noise of the piston are great. Therefore, it is easy to wear out the sleeve after being used for a short term.
Therefore, the invention provides an air pump to mitigate or obviate the aforementioned problems.